1. Field of the Invention
The present invention relates to an intake insulator, and more particularly to an adiabatic intake insulator inserted into a portion for connecting a carburetor to such as a small two-cycle gasoline engine or the like.
2. Description of the Related Art
Generally, in a small two-cycle internal combustion engine used for a mower or the like, an adiabatic intake insulator, which is made of synthetic resin material such as phenolic resin through injection molding for instance, is inserted into a portion for connecting a carburetor to a cylinder or a crank case of an engine. FIG. 5 shows a lateral cross-sectional view of a conventional intake insulator with the above construction. The intake insulator 1 comprises: carburetor securing portions 10 for supporting and securing a carburetor which is situated on the left side of FIG. 5 and is connected to a left end face of the intake insulator; portions 20 for securing to a cylinder of an engine which is located on the right side of FIG. 5 and contacts a right end face of the intake insulator 1; and an intake passage 15 through which air-fuel mixture from the carburetor is introduced to the engine.
Through holes 12 are formed in the direction parallel to the intake passage 15 of the intake insulator 1, and a bush 11 made of brass or the like with a female thread portion on the inner wall thereof is molded into each of the through holes 12 to provide the carburetor securing portion 10. A bolt for supporting and securing the carburetor is inserted into each of the through holes 12 from the left side and is engaged with the bush 11. Each of the portions 20 for securing to the cylinder comprises a through hole 21 for a bolt extending in parallel to the intake passage 15 of the intake insulator 1, and a counterbore 22 in which a head of the bolt is accommodated. Further, the intake passage 15 is formed at the center of the intake insultor 1 with the inner diameter thereof is gradually enlarged toward the cylinder side.